An amplifier is an important device commonly used in the transceiver module in various wireless communications, including cellar and satellite communications, as well as wireless local area network. A typical amplifier is implemented utilizing a signal-gate and dual-gate field-effect transistor (FET) device, such as a high-electron mobility transistor (HEMT) device or a pseudomorphic HEMT (pHEMT) device, as a transconductance amplifier. As to the dual-gate device, an input radio-frequency (RF) signal is applied to a first gate of the dual-gate FET device. The amplified signal is then drawn from the drain electrode of the dual-gate FET. A DC bias voltage is applied to a second gate of the dual-gate FET, so that the device gain can be controlled. It noteworthy that not only the input RF signal but also the noise would be amplified in the input stage, so that both the gain performance and the noise figure are important considerations for such amplifiers.
It has shown that conventional dual-gate HEMT device demonstrates excellent microwave gain performance, due to its high output resistance and low feedback capacitance, as compared with single-gate HEMT devices. However, the three-port cascode topology of a dual-gate device, which requires another DC bias from an external voltage source, further complicating the device testing and modeling, and isn't suitable for packaging mold of two-port single-gate discrete microwave device.
In order to facilitate device testing, modeling, and packaging without modification of the baseline of single-gate HEMT epi-structure, there is a need for developing a dual-gate HEMT device, which transforms the conventional three-port cascode topology into a two-port dual-gate device.